On The Safety of Allergy Shots or Why Can’t I Do This At Home

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Primum non nocere– First, do no harm- Hippocrates

Most treatments in medicine are a balance of safety and effectiveness, risk and benefit. Allergy shots are no different. When done properly, they can be life-changing. They do, however, carry some risk, and they are not a process which should be entered into or performed cavalierly.

Allergy shots work by giving patients injections of the things to which they are allergic. So, if you are allergic to ragweed and cat, your shots will contain ragweed pollen and cat allergens. By starting with a very tiny dose and gradually increasing the dose over time, your body learns to tolerate the allergens in the shots. Numerous studies have shown that allergy shots have a dose threshold that must be reached in order for desensitization to occur. In English, this means that if you don’t put enough allergen in the vials, the shots don’t work. Allergists call this dose the maintenance dose.

Building a patient up to the maintenance dose is a double-edged sword: the higher the dose, the greater the chance of desensitization, but also the greater the chance of having an allergic reaction to the shots. Allergists have learned how to minimize the risk of reactions in a number of ways. First, we use maintenance doses that offer the best combination of effectiveness and risk. Second, we use build-up schedules that mitigate risk while allowing the patient to reach maintenance in a reasonably timely manner. Third, we have dedicated staff and computerized protocols to ensure that patients are getting the right dose every time. Fourth, our staff look for patients having issues with their shots so that appropriate dose adjustments can be made. Finally, we monitor our patients after every shot for signs of a reaction and we treat them promptly and appropriately when they occur.

So what is the chance you’ll have a reaction to your allergy shots and how bad can it be? In broad terms, the risk of systemic reactions is low, but serious reactions, including life-threatening reactions and fatalities, have occurred. Estimates are that 3-5% of patients on a conventional build-up schedule will have a systemic reaction. The majority of these are mild, fortunately. In a review of our practice a few years ago, I calculated that we gave epinephrine to a shot patient for a bad allergic reaction around once a month. This came out to roughly once for every 5000 injections, a rate which is consistent with most large studies looking at systemic reactions in allergy shots. Large, long-term studies estimate the fatality rate at one every 2.5 million injections, which is about the same risk as being in a fatal commercial airline crash, one out of every 2.5 million flights.

If the risk is that low, then why can’t patients get their shots at home? Simply put, the convenience is outweighed by the risk. The reason allergy shots are so safe in the first place is because patients don’t get their allergy shots at home. The expertise, monitoring, and access to prompt evaluation and treatment that prevent¬†mild-to-moderate reactions from progressing to severe, life-threatening reactions are the primary reasons that allergy shots are as safe as they are. If you removed these, then the safety profile of allergy shots would be much worse. This is why the guidelines for allergen immunotherapy set forth by the American Academy of Allergy, Asthma, and Immunology and the American College of Allergy, Asthma, and Immunology explicitly state that injections must be given in an appropriate clinical setting with a provider on site and the means to diagnose and manage acute allergic reactions, and that patients must be observed for an appropriate length of time after injections. Physicians who allow their patients to receive allergy injections at home are operating outside of published guidelines, are not following the standards of practice in the community, and are placing patients at risk.

Our practice has multiple locations, early and late shot hours and even, in a few offices, weekend hours, all to try and make the shot process as convenient as possible for patients while maintaining the highest degree of safety for you and your children. You should accept nothing less.

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